Hall cell position sensor for outboard drive apparatus

ABSTRACT

Apparatus for power positioning and holding of an outboard marine drive includes a manual trim angle selection input signal generator. A position sensitive signal generator in the form of a Hall cell or a resistor is secured on the gimbal ring unit with a movable element set in accordance with and by the movement of the marine drive. A comparator provides a pair of output signals in accordance with the relative magnitude of the two signals and depending upon whether drive is to be raised or lowered. The output signals are similarly connected through amplifying and switch isolating circuitry to actuate an electric motor and hydraulic pump unit to raise or lower the stern drive until the position sensor and the manual input are nulled. A slight dead band maintains stable operation as the stern drive is moved to a new trim position. A fail-safe circuit prevents malfunctioning if the sensing system open circuits.

United States Patent [191 Hager et a1.

Related U.S. Application Data [62] Division of Ser. No. 329,726, Feb. 5,1973, Pat. No.

[52] U.S. C1 307/309; 114/144 A, 115/34 R; 115/41 R; 115/41 HT [51] Int.Cl....... H0lr 5/00; B63b 41/00; B60q 1/26 [58] Field of Search 307/278,309; 1 14/144 A, 114/144 R, 235 B; 115/34 A, 34 R, 41 R, 41

[56] References Cited UNITED STATES PATENTS 3,641,965 2/1972Schmiedel...................... 115/41 HT 3,688,133 8/1972 Flachsbarth307/309 3,739,738 6/1973 41144 R luutmn l t I r l I l [451 July 8,1975

Primary Examiner-Stanley D. Miller, Jr. Attorney, Agent, or Firm-Andrus,Sceales, Starke & Sawall 57] ABSTRACT Apparatus for power positioningand holding of an outboard marine drive includes a manual trim angleselection input signal generator. A position sensitive signal generatorin the form of a Hall cell or a resistor is secured on the gimbal ringunit with a movable element set in accordance with and by the movementof the marine drive. A comparator provides a pair of output signals inaccordance with the relative magnitude of the two signals and dependingupon whether drive is to be raised or lowered. The output signals aresimilarly connected through amplifying and switch isolating circuitry toactuate an electric motor and hydraulic pump unit to raise or lower thestern drive until the position sensor and the manual input are nulled. Aslight dead band maintains stable operation as the stern drive is movedto a new trim position. A fail-safe circuit prevents malfunctioning ifthe sensing system open circuits.

6 Claims, 8 Drawing Figures PMEHTED L 8 I975 8 94 2 5 0 SHEET 1 HALLCELL POSITION SENSOR FOR OUTBOARD DRIVE APPARATUS This is a division ofapplication Ser. No. 329,726, filed Feb. 5, 1973 and now US. Pat. No.3,834,345.

BACKGROUND OF THE INVENTION This invention relates to automaticpositioning drives for angular positioning of an outboard drive unit.

Outboard propulsion drive units are widely employed for marine drivesparticularly of the smaller pleasure boats and the like. Such units arepreferably connected to the transom of the boat and mounted for angularorientation about a vertical axis for steering purposes and about ahorizontal axis to permit optimum location of the propulsion unit in thewater for optimum driving conditions. Hydraulic systems have beenadvantageously applied to power trim positioning of the out boardpropulsion units. For example, US. Pat. Nos. 3,434,448 and 3,434,449disclose hydraulic systems wherein a piston and cylinder means iscoupled to a stern drive for selectively positioning and holding of thestern drive unit in various angular orientation about a horizontal axis.The hydraulic system is driven from a suitable electric motor drivenpumping unit having an appropriate hydraulic control system for raisingand lowering of the stern drive unit. Generally such systems haveemployed a manual control at the steering station which the operatorcontinuously operates until such time as the motor is at a desiredposition. The prior systems have therefore relied on the operatorsensing an optimum condition. Alternatively, meters have beenelectrically coupled to the stern drive unit and positioned inaccordance with the angular drive trim position. The variable resistorunit is connected in the circuit of a meter mounted adjacent to theoperator and provides a visual indication of the angular setting timeposition.

Although the prior art devices have permitted power trim positioningsystems, they have relied upon the direct attention of the operatoreither through a subjective sensing of optimum motor positioning, visualviewing of the motor position or of a meter with adjustment of the trimuntil an optimum condition is believed to have been established. Thus,the operators attention is, in essence, divided between the setting ofthe trim control and the operation of the propulsion unit. Further, insuch systems, the set trim position changes during operation such as aresult of interaction with the water and/or objects in the water or as aresult of minor hydraulic leakage. For example, rapid acceleration orrunning over a stump or the like may cause the marine propulsion unit tomove from the set position without necessarily returning to the setposition after disturbing forces are removed. The operator must,therefore, provide a more or less continuous attention to the trim runpositioning of the propulsion unit. This may require the operator'sattention under conditions representing a hazardous diversion from thedriving of the boat.

SUMMARY OF THE PRESENT INVENTION The present invention is particularlydirected to a power lift system for automatically setting the marinepropulsion unit in a selected trim position as a result of a singleangle selection input, with the system holding the trim position for allnormal operating conditions. Generally, in accordance with the presentinvention,

the automatic trim system includes a manually actuated signal generatorfor producing a signal related to a desired trim angle. An automaticsensing unit is coupled to a power unit and generates an output signalproportional to the angle position with respect to a reference. The twosignals are connected to a comparator, the output of which provides anoutput for raising and lowering of the propulsion unit. The comparatorpreferably provides a pair of on-off signals for selectively raising andlowering of the marine propulsion unit. Thus, the one signal actuates apower lift mechanism to raise the stem drive and the opposite signalcorrespondingly actuates the power lift unit to lower the marinepropulsion unit. The drive unit is thus automatically positioned until anull signal condition is established, at which time the drive unit isheld in the preset desired position. If the trim angle should be changeddue to any operating condition, the system will automatically repositionthe drive unit to the preset condition.

In accordance with a further novel aspect of the invention, theapparatus is provided with a time delay which will be sufficient to keepthe system from selfcorrecting itself under minor disturbances such asthose associated with wave bounce and the like. The apparatus mayfurther include a pressure responsive cutout which opens the driveposition circuit if a high pressure is applied to the propulsion means,such as encountered if passing over a log. This permits the standard logjumping" with subsequent automatic reconnection of the trim control.Further, electronic circuitry can be employed to minimize the powerconsumption by the control system and thereby adapt the unit to theusual marine drive system.

The system, in accordance with a particularly novel aspect of thepresent invention, includes a dead band selected in accordance with thecoasting characteristics of the drive unit including the hydraulicsystem. The dead band is selected to prevent overlap between adjacentselected angles.

In accordance with a further novel aspect of the present invention, theposition sensor is a Hall cell sensor including a Hall cell transducerin combination with a magnetic member, with the cell and magnetic unitmounted for relative movement as a part of the drive unit. The Hall cellsensor transduces the sine wave of flux density to a related sine waveof voltage in response to the relative angular orientation of the Hallcell and the magnetic unit. The output is amplified and preferablybuffered with a pair of emitter follower transistors to produce adouble-ended output sufficient to drive an operational amplifier, theoutput of which is connected as an input to a comparator amplifier. Thesensor circuitry includes filtering means to attenuate any radiofrequency signal resulting from the ignition system of the marinepropulsion unit and an offset adjustment means to adjust the offset ofthe Hall device. The system is preferably powered from a suitablevoltage regulator means.

The Hall cell amplifier and emitter follower circuit may advantageouslybe formed as an integrated circuit unit with the Hall cell mounted infixed relation to the propulsion drive unit. A doughnut shaped magnet issecured to the movable portion of the stern drive, for example, to thepivot shaft mounting and is rotated about the Hall cell to impress anoperative flux upon the Hall cell which varies as a sine wave with therotation or angular orientation of the propulsion drive unit. Thecomparator and drive circuitry may be separately mounted in a suitablecontrol mounted inboard of the motor of the boat. Thus, in the preferredcircuitry an operational amplifier means including a separate pair ofoperational amplifiers is connected as a comparator to compare theoutput of the Hall cell sensor and a preset DC signal. The output of oneoperational amplifier is connected to selectively drive an up switchingamplifier and the output of the other operational amplifier is connectedto drive a down switching amplifier. The outputs of the switchingamplifier are connected through suitable relays or other switching meansto reversibly drive an electric motor. The electric motor, in turn, iscoupled to reversibly drive a hydraulic pump unit for correspondingraising and lowering of the propulsion drive unit until such time as theposition sensing signal is nulled with the input signal. The controlcircuitry may further include a stabilizing network to eliminate theeffects of vibration and to insert the desired angular dead zone whichwill permit the drive unit to coast past the equilibrium position byapproximately one degree in either direction without re-energization ofthe system.

Further, as previously noted, the US. Pat. 3,641,965 discloses aresistive sensor for providing an output signal proportional to theangular orientation of the drive unit. As noted therein relativelysimple and inexpensive linear resistors are preferably employed.However, the output as noted is linear with the position and,consequently, such an inexpensive resistor does not provide the requiredsine wave signal compatible with a system employing a Hall cell sensor.Applicant has found, however, that for the limited angular positioningrequired of a marine propulsion unit, a linear resistor in series withan appropriate fixed resistor generates a variable voltage whichapproaches a sine wave voltage versus angular displacement and is suchas to permit highly satisfactory operation as the input to the Hall cellsignal processing circuit. The resistive sensitive system may bedesirable to minimize the expense and to avoid certain temperaturestabilization required with Hall cell units.

As the sensing systems are preferably mounted to the propulsion unitthere is a danger that the circuit will become open circuited due towear or water contamination, corrosion or the like, particularly wherethe resistive sensing network is employed. Under such conditions thevoltage may rise to provide a turn-on signal to the power lift meanstending to lower the propulsion drive unit to its maximum down positionwith no means for the operator to return it to a higher position. Thiscan obviously create an extremely dangerous operating conditionparticularly when the boat is under power. The present inventiondesirably provides a safety circuit to positively prevent the operationof the lowering power circuitry under open circuit conditions. Thesafety circuit in accordance with a further novel aspect of the presentinvention may employ a Zener diode means or the like connected to sensethe input voltage from the resistance position sensor and actuate aninterlock switch such as a transistor in response to an open circuitcondition. The interlock switch positively prevents energizing of thelowering circuitry. The same voltage signals holds the lifting circuitin the preferred construction. The safety circuit preferably includes anintegration means such as a resistor-capacitor to produce a delay in theactuation of the fail-safe circuit and thereby permit a momentary opencircuit condition. Thus, in the resistance sensor element, the wiper maymomentarily create an open circuit condition when moving from onewinding turn to the next and erroneously operate the safety circuit if adelay means is not introduced.

The present invention thus provides a reliable automatic drive foraccurately locating and positioning of an outboard marine propulsiondrive unit.

BRIEF DESCRIPTION OF THE DRAWINGS The drawings furnished herewithillustrate preferred constructions of the present invention in which theabove advantages and features are clearly disclosed as well as otherswhich will be readily understood from the following description:

In the drawings:

FIG. 1 is a side elevational view of an inboardoutboard drive unitmounted on the transom of a partially shown watercraft, with varioustrim positions shown in phantom line illustration;

FIG. 2 is a fragmentary rear view of the watercraft and stem drive unitshown in FIG. I;

FIG. 3 is an enlarged fragmentary side elevational view of the sterndrive unit shown in FIG. 1 more clearly illustrating the Hall cellmounting;

FIG. 4 is a vertical section taken on line 4-4 of FIG.

FIG. 5 is a block diagram of an automatic trim control systemconstructed in accordance with the present invention and applied tocontrol a stern drive unit such as shown in FIG. 1;

FIG. 6 is a schematic circuit diagram of a system corresponding to thatshown in FIG. 5 and employing a Hall cell position sensor mounted as apart of a stern drive unit shown in FIG. 1;

FIG. 7 is a schematic circuit similar to FIG. 3 illustrating anembodiment employing a resistance sensor and a novel fail-safe circuit;and

FIG. 8 is a schematic circuit of a simple differential relay embodiment.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT Referring to the drawings andparticularly to FIG. 1, an outboard propulsion unit or assembly in theform of a stern drive unit 1 is shown mounted on the transom 2 of apartially shown watercraft 3. The stern drive includes a lower driveunit 4 and a bracket mounting assembly 5 for movably mounting andsupporting of the drive unit from the transom 2. The bracket assembly 5includes an intermediate gimbal ring 6 which pivotally supports thedrive unit 1 upon a generally transverse horizontal axis 7 for selectivetilt movement of the unit in a generally vertical plane. The gimbal ring6 is in turn pivotally supported on a generally vertical axis 8 by theouter transom bracket 9 to provide for and permit movement of the driveunit 4 in a generally horizontal plane for purposes of steering themovement of the watercraft 3.

The drive unit 4 more particularly includes the usual propeller 10 whichis drivingly connected to an engine 1 I mounted inboard of thewatercraft 3. The propeller 10 is selectively rotatable in oppositedirections in accordance with operation of suitable reversing gearpositioning means not shown to provide for a corresponding forward andreverse thrust respectively for the watercraft 3. Further, the drivecontrols include a suitable remote speed and directional control unitconnected by an electrical, mechanical cable system or the like notshown to permit convenient location of the operation, for example,adjacent a forward control station 12 of the watercraft 3. In addition,hydraulic power means are provided for supplying hydraulic liquid to apair of cylinder piston means l3 connected to the opposite sides of thestern drive unit 1 functioning as hydraulic shock absorbing means aswell as stern drive angular positioning or trim positioning power means.Thus, as more fully described in the previously referred to US. Pat.Nos. 3,434,448 and 3,434,449, the piston-cylinder means 13 are connectedto a hydraulic gear pump 14 which is reversible driven by a reversibleelectric motor 15 to selectively supply liquid to the opposite sides ofthe cylinder-piston means 13, thereby permitting the powered extensionand retraction thereof with a corresponding angular orientation orpositioning of the stern drive unit 1 about the horizontal axis 7. Asthe above mounting and positioning of the stern drive may take anydesired form and construction, no further description thereof is givenother than that necessary to clearly describe the present invention.

In the operation of a watercraft which is driven from an outboardpropulsion means such as a stern drive unit, the watercraft ispreferably started with the drive unit 1 in the lowered depending fullline position shown in FIG. 1. This aids the movement of the boat to theplane position. However, when the boat is on a plane, it is desirable tore-position the drive unit 1 further outward for maximum efficiency andspeed as disclosed in the previously referred to US. Pat. No. 3,641,965.Under normal operating conditions various trim angles might be desirablyemployed. Further, the drive unit 1 may be raised upwardly to maximumposition for trailing or low power operation. The present invention isparticularly directed to provide an automatic drive and positioningcontrol system which will permit selection of a given angle and theholding of such given angle automatically and in response to theoperator merely actuating a suitable input positioning device to aselected angle position without the necessity for continued attentionand monitoring of the system. Thus, generally, in accordance with thepresent invention, a trim angle selection unit 17 is provided adjacentto the operating station 12 and may conveniently be in the form of amultiple switch unit adapted to select any one of a plurality ofpreselected angles between a reference zero position and a maximumraised position. Thus, for example, a highly satisfactory automaticcontrol system has been constructed providing for the selection of theseven different angles of 0, 35, 7.0", l0.5,l5, 22 and 44. Althoughpushbuttons, levers or position selection means can be used, asatisfactory selection unit 17 has been constructed with a rotary switchhaving an input knob 18 that could be moved to any one of the anglepositions. The trim control system further includes a stern driveposition sensitive signal means 19 coupled to the unit I and the signalsof the selection unit 17 and signal means 19 are compared and processedto automatically and directly establish the angular movement andpositioning of the stern drive unit 1 and is continuously operative tomaintain such trim angle position.

Referring particularly to FIG. 5, a block diagram of the automatic trimcontrol system of the invention is illustrated in which the manual inputcontrol 17 is shown providing one input to a comparator amplifier 20,the opposite input of which is connected to the position sensor 19. Theoutput of the position sensor is a signal directly related to theangular positioning of the drive unit 1 and of a character related tothe signal from the unit 17. The comparator 20 compares the two signalsand provides a lift signal or a drop signal at a pair of correspondinglines 21 and 22, depending upon the relative magnitude of the two inputsignals. Thus, if there is a difference between the selected angle andthe actual angle, a signal will appear at one or the other of the twooutput lines. These signals are similarly processed and in particularthe control signal is amplified through similar amplifiers 23 and 23aand connected to actuate and up-relay 24 or a down-relay 25. The relays24 and 25 in turn connect power to the electric motor 15 to reversiblyoperate the electric motor in accordance with the operation of therelays to thereby reversibly drive the hydraulic pump 14. The controlsystem will automatically establish the trim angle and will reset thetrim angle if it is changed for any reason under operation; for example,due to rapid acceleration, running over a stump or the like. Theoperator can select any one of the given angles without a great deal ofattention or distraction from the normal operation of the watercraft.

Referring particularly to FIG. 6, schematic circuit diagram of anautomatic trim control system is shown employing a Hall cell positionsensing unit coupled to the stern drive unit, as shown in FIGS. 1-4 andfunctioning as a position sensor.

The Hall sensor 19 preferably is constructed as an integrated Hall cellcircuit unit having a Hall cell 27 connected to a closely regulatedpower supply 28. A resistor-capacitor network 29 connects the supply 28to the battery 29a and functions as a low pass filter to attenuate radiofrequency that might be produced by the ignition system, not shown.Thus, in a practical application, the Hall cell was connected to a 5.6volt regulated voltage.

The output of the Hall cell 27 is connected to a differential amplifier30 which produces a double-ended output, each of which is coupledthrough a buffering emitter transistor 31 to a second amplifier 32 toprovide an amplified voltage signal related to the Hall cell voltage atthe output line 320. A pair of resistors 33 one of which is madeadjustable, is connected to the input of the differential amplifier 30to adjust the offset of the Hall device 27. The several circuit elementsof the sensor 19 are, as noted, preferably formed as a single integratedcircuit.

The output of the Hall cell 27 is controlled by an annular permanentmagnet 34 which as shown diagrammatically in FIG. 6 is polarizeddiametrically of the magnet on a line generally normal to thediametrical line through the Hall cell. The magnet 34 is mounted forangular rotation about its own axis and is angularly oriented withrespect to the Hall cell 27, as more fully shown in FIGS. 3 and 4. Theeffective component of the flux impressed upon the Hall cell 27 changesor varies in accordance with a sine wave function as the angularorientation or position of the magnet 34 with respect to the Hall cell27 changes. The Hall cell 27 thus transduces the sine wave of magneticflux to a corresponding sine wave voltage signal.

As illustrated in FIGS. 3 and 6, for the lowermost position of the driveunit 1, the Hall cell 27 is aligned with the periphery of the magnet 34at essentially ninety degrees to the north and south poles. Althoughthis is not the position of maximum flux and therefore signal level, itis the position of the maximum rate of signal change for any given smallangle movement. This is particularly advantageous when applied topositioning of a marine drive unit, which is normally positioned betweena vertical or position and a raised 55 position. The angular positioningbetween approximately 0 and l is quite significant in the propulsion ofan outboard unit and consequently maximum accuracy is desired in thatrange. The sine wave voltage signal provides maximum voltage change perdegree at the zero crossover axis as a result of the maximum slope andalmost linear characteristic of the wave at that point. This alsopermits use of a relatively narrow voltage range; for example, 2.5 voltsfor the zero degree angle setting to 8.2 volts for a maximum or 55 anglesetting. Although the voltage change per degree of angular movement inthe upper range or last l5 is substantially less, the angular positionis not as significant for operating the propulsion means and istherefore readily employed.

The output of the cell 27 is amplified and coupled through the emitterfollowers 31 to prevent loading of the sensor circuit. The amplifiedoutput is impressed upon a second amplifying stage 32 through seriescoupling resistors 35 and 36 and a resistor 37 to ground which sets thesource impedance of the second amplifying stage. A paralleled RCfeedback network includes a variable resistor 38 and a fixed capacitor39. The variable resistor 38 permits adjustment of the gain of thesecond amplifying stage while the feedback capacitor limits the bandwidth of the operational amplifier and protects it from spuriousoscillation.

The output is thus an amplified signal, taken with respect to ground,which is directly related to the angular orientation of the stern driveunit 1 with respect to the zero or reference position.

The output is applied as one input to the comparator 20, which, as shownin FIG. 6, is preferably an operational amplifier means including a pairof operational amplifiers 40 and 41 for driving of the respectiveswitching amplifiers 23 and 23a. Each of the amplifiers 40 and 41 issimilarly constructed and includes a corresponding non-inverting input42 and 43 and an inverting input 44 and 45. The non-inverting input 42and the inverting input 45 are connected through individual seriescoupling resistors 46 and 46a to the ungrounded output of the anglesection unit 17. Individual coupling resistors 47 and 47a connect theinverting input 44 and the non-inverting input 43 to the sensor 19. Thesensor connected input terminals 43 and 44 of amplifier 40 and 41 arefurther connected to ground through suitable bypass capacitors 48 which,with the coupling resistors define low pass signal filters in the inputcircuit.

The selection unit 17 includes a voltage dividing network including afixed resistor operational connected to the battery 29a with a regulatedpower supply 50 providing a regulated voltage to the selection unit 17and the comparator circuit 20. The opposite leg of the voltage dividingnetwork includes the rotary switch assembly having a movable contact 51selectively engaging one of seven different contacts 52, relatedsequentially to the trim angles 0, 35, 7, l0.5, 22 and 44 in accordancewith the system heretofore discussed. Each of the contacts 52 isindividually connected to ground via an angle related resistor 53 tocomplete the voltage dividing network, with the common connection orjunction 530 between the fixed resistor 49 and the movable contact 51connected to the inputs 42 and 45 of the opeational amplifier 40 and 41.Thus, each of the resistors 53 provides a different voltage division ofthe regulated voltage with a corresponding fixed reference or setvoltage input to the operational amplifier. The sensor and the referencevoltages are thus applied to both operational amplifiers 40 and 41,compared, and an appropriate output signal generated to null the systemby repositioning of the stern drive unit.

The operational amplifier 40 includes a paralleled R-C feedback network54 which interconnects the amplifier output line 55 to the non-invertinginput 44. A similar R-C network 54a interconnects output line 56 ofamplifier 41 to the non-inverting input 45. The capacitors of thefeedback networks 54 and 54a limit the frequency response of theamplifier in order to prevent a frequency response high enough to causepositive feedback and unstable operation. The feedback resistors of thenetworks 54 and 54a in combination with the input resistors set the gainof the amplifier which is selected to be sufficiently high to maintainalternative full on and full off conditions at the lines 55 and 56 andprovide a switching logic to the drive portion of the power tiltmechanism. A relatively low voltage appears at lines 55 and 56 withamplifiers 40 and 41 off and a relatively high voltage appears when suchamplifiers are on: In a practical system, the voltage may change from2.4 volts to 7 volts.

Thus, selection resistors 53 are selected to maintain the minimumvoltage applied to the operational amplifier well below the low voltageoperating limit at 0 centigrade, to thereby avoid possible erroneousoperation with temperature. The stem drive unit is a relatively largeload and will coast somewhat after a null condition is created. Inaccordance with an aspect of this invention, a dead band is introducedinto the input circuit to allow for such movement. In the illustratedembodiment, a dead band bias voltage is established at the invertinginput 45 of amplifier 41 and at the noninverting input 42 of amplifier40. The input 45 is connected by a resistor 57 to the regulated powersupply 50 while the noninverting input is connected by a resistor 58 toground. The resistor 57 and 58 are selected such that the referencevoltage is offset slightly and results in a slightly premature cutoff ornulling of the corresponding amplifier. The dead band is selected inaccordance with the coasting characteristics of the stern drivemechanism and in accordance with a practical construction permits thestern drive unit to coast past an equilibrium position by one degree ineither direction without afi'ecting the system.

For example, the reference voltages inserted by resistor 53 may beselected to vary the input voltage between 2.4 and 7 volts, with theresistors 57 and 58 causing the actual input voltage to be offset by 0.1of a volt. Thus, if the selection unit is set to an intermediateposition with four volts appearing at line 53a, the voltage at thenon-inverting input 42 of the raising operational amplifier 40 would be3.9 volts while the voltage at the lowering operational amplifier wouldbe 4.1 volts. If the sensor output voltage is, for example, below suchlevel as a result of the drive unit 1 being located below the selectangle, the amplifier 41 remains off. The amplifier 40, however, isdriven on because the inverting terminal 44 is at a lesser voltage thanthe non-inverting terminal 42. The unit 1 is driven up and the sensorvoltage increases until a voltage 3.9 volts is impressed on bothapplifier 40 and 41. Amplifier 41 is off and remains off. This, however,nulls the output of amplifier 40 which then cuts off and terminates thepositive drive. The drive unit 1 continues to coast toward the setposition and stops. If it coasts slightly past the set positioncorresponding to the reference voltage of the selection unit 17, theoffset of such voltage appearing at the opposite terminal preventsdriving of the operational amplifier on, unless of course the coastingis excessive. in that case, the voltage output of sensor 19 compared tothe set voltage differs by more than the offset voltage and reverses thedrive.

For example, assume the coast is four degrees and thus in excess of twodegrees dead band. The sensor voltage is then 4.3 volts equal to 3.9volt cutoff voltage and the additional 0.4 volts for the 4 coastmovement. The non-inverting input 43 of the lowering amplifier 41 is nowabove the set voltage of 4.l volts at the inverting terminal 45. As aresult, amplifier 41 turns on and reverses the drive to properlyre-position the drive unit 1.

Generally, the stern drive units of the assignee of this application arebasically of two different varieties. One employs a relatively hydrauliccylinder means and moves at a relatively fast angular velocity, with atotal angular displacement of about 50. The other system illustratedemploys a somewhat larger hydraulic cylinder means moving at a somewhatslower angular velocity but with a total angular displacement of about56. This difference in velocity results in a somewhat different amountof average coast and generally it has been found that the slower dualdrive will stop approximately three-quarters of a degree before thedesired position whereas the single drive will stop at approximately thedesired position with the 2 dead band.

The amount of coast also depends on the amount of power applied to thepropeller. Thus, with the stern drive trimmed down and under fullforward power, the total coast may be such as to move beyond the deadband zone. However, with the present invention, the system will correctitself once and come back within the desired position.

The total dead band zone of two degrees in the system described is thusa compromise to adapt the unit to both systems while maintainingseparation of the two adjacent trim settings at 3.5.

The difference in total angular displacement also requires somewhat of acomprise is a single system is to be applied to all the drives. Further,some margin of safety must be introduced into the system in order tocompensate for normal manufacturing tolerances and the like as well asto allow a few degrees between the all down trim position and the alldown mechanical stop. A practical system was designed for a variation intrim position between zero and forty-four degrees nominal. As apractical matter, the actual positions may, as a result of normalmanufacturing tolerances and the like, vary between 40 and 48 from unitto unit. If close tolerance components are employed for the highestvalue sensing resistor as well as the interrelated voltage dividing andsensing resistors of and for the voltage regulator diode and the like,the variation can be substantially reduced. Thus, if one percenttolerance parts were employed, the system could be designed for nominaldisplacement of approximately forty-seven degrees with an expected totalvariation from unit to unit of about from 46 to 48.

Alternatively, the control circuits could be constructed for eachparticular stern drive by a proper selection of the bias resistivenetwork to the comparator. The highest value position resistor 53 aswell as the compensating dead band resistors 57 and 58, for example,could be properly selected for each design. This, of course, wouldrequire inventory of two separate control circuits, with the attendantexpense and the like. The resistors 57 and 58 thus may be adjusted toprovide a desired response to the inputs of sensor 19 and selectivemeans 17 as applied to the amplifiers 40 and 41 of stage 20.

Sensor assembly 19 and comparator 20 are powered from the regulatedsupply 50 to provide reliable logic response. The regulator 50 may beany suitable construction, such as a Zener diode unit with a temperaturecompensating diode and stabilizing capacitors to produce the desiredregulated voltage. The regulator 50 produces the desired operatingvoltage such as 9.2 volts.

The amplifier output lines 55 and 56 are similarly coupled to high gainamplifying and switching stages 23 and 23a which function as powerswitches and are shown as Darlington switching circuits. As each of theoutput lines is similarly connected, that for the raising or up line 55is described, with the corresponding elements for the lowering circuitbeing identified by similar prime numbers.

The illustrated amplifier 23 includes a pair of transistors 61 and 62which are connected as a Darlington pair, with the input base connectedby a coupling resistor 63 to the comparator output line 53. A turn-onresistor 64 is connected between the base and the ground and emitter tocomplete the input signal circuit. The resistors 63 and 64 form avoltage divider which reduces the base voltage at the amplifier 23 belowthe switching level with the operational amplifier 40 off, and applyingthe relatively low voltage signal.

The output is taken at the collector with a negative feedback networkincluding capacitor 65 which introduces a time constant in the systemwith a delayed turnon and rapid turn off to prohibit the system fromcorrecting itself from each slight variation in position of the sterndrive unit, such for example as associated with slight wave bounce. Theswitching and associated feedback circuit is more fully described in thecopending application of James Hager and no further description is givenherein.

The output switching as provided by the Darlington circuitry providesselective completion of the circuit to the relay 24, which has a winding67 connected in series with the output circuit of the Darlingtontransistor unit to the battery power supply. The Darlington pairnormally presents a high impedance or open circuit condition to therelay winding. When the Darlington pair is turned on, as a result of thetumon signal at the output line 55 of the amplifier 40, the Darlingtonconnected transistors rapidly switch to full on to establish a very lowimpedance path thereby completing the energizing circuit through therelay winding. This, in turn, closes the related relay contacts 67-1 toprovide power to the motor for energizing of the electric motor in alift direction and thereby driving the pump 14 to power the hydraulicsystem to correspondingly raise the drive unit 1. As the drive unit 1raises, the magnet 34 is correspondingly positioned and varies theeffective flux supplied to the Hall cell 27 and correspondingly changesthe voltage signal to the comparator 20 when the sensed signalcorresponds in a predetermined manner to the set signal as determined bythe positioning of unit 1.

If for any reason the drive unit 1 moves from the set position, the Hallcell 27 generates an offset signal to operate the relay 24 or 25. If thestern drive unit 1 is above the desired position, a signal appears atoutput line 56 which turns on the Darlington transistors 61' and 62' andcompletes the power circuit to the lower relay winding 68. This, inturn, results in the closing of the associated contacts 68-1 to energizethe electric motor to operate in the opposite direction with thehydraulic pump 14 oppositely actuated to introduce hydraulic fluid intothe piston-cylinder means 13 to lower the stern drive unit 1.

When the unit is again in the preset position, the magnet 34 isrelocated with respect to the Hall cell 27 to establish a null conditionto turn off the trim drive and establish the stable condition.

The operator may therefore conveniently control the trim position beforeand during running.

The Hall cell sensor 19 of FIGS. 5 and 6 is preferably constructed as asmall compact and potted assembly which is mounted to the stern driveunit 1, as most clearly shown in FIGS. 3 and 4. A cup-shaped dischousing 70 includes a plurality of outer arcuate mounting slots 71 and72 and is secured abutting the gimbal ring or member 6 by suitable capscrews 73 and 74 passing through the slots 71 and 72 and threaded intoappropriately tapped openings 75 in the member 6. The housing 70includes a central opening aligned with the horizontal shaft 76 which isrotatably journaled in the gimbal ring and defining the tilt axissupport of the drive unit 4. The housing 70 includes a cylindricalrecess or chamber 77 in the exterior face with a peripheral inner wall78 of stainless steel or other similar nonmagnetic material. The Hallcell 27 and associated circuitry of unit 19 shown for example in FIG. 6is located within the recess 77 which is then filled with a suitablepotting material 79 such as an epoxy resin to physically support theelements and protect them from the severe environmental conditionsencountered in marine use. The Hall cell 27 is diametrically locatedwith respect to the shaft opening 75, as shown in FIG. 4. The annular ordoughnut shaped magnet 34 is secured to the shaft 76 by a clamping nut80 and located within the central opening of wall 78 of the housing 70,particularly in a common plane with the Hall cell 27. The magnet isdiametrically polarized to establish a radially outwardly directed fluxwhich is impressed upon the Hall cell 27. Thus, the nonmagnetic innerwall readily transmits the flux to the potted Hall cell. As described inconnection with FIG. 6, a sine wave of flux is applied to the Hall cellin accordance with angular orientation of the drive unit with respect tothe gimbal ring or member 6. A cover 81 may be secured to the housing toenclose the potted recess and the magnet.

If desired, the system can be employed with a resistance sensingelement, similar to that described in U.S. Pat. No. 3,641,965 in placeof the Hall cell 27. FIG. 7 is a schematic circuit corresponding to thatof FIG. 6 with the substitution of a resistor position sensor 81 for theHall cell unit 19 described above and additionally with a fail-safecircuit 82. Corresponding elements of FIGS. 6 and 7 are correspondinglynumbered and no further description of the circuit is given other thanto clearly describe the revision to the basic circuit. The resistorposition sensor 81 includes a resistor card 83 with a movable wiper 84rotatably mounted to scan the card. A wound resistor 85 is mounted onthe card and connected between the ground and the input terminal of theoperational amplifier 40 functioning as the comparator. The wiper 84inturn is connected to the corresponding input and thus selectively shortsa portion of the resistance from the circuit and simultaneously adjuststhe voltage impressed on the input terminal. The wiper is coupled torotate with drive unit 4, for example, by connection to shaft 76 asdisclosed in U.S. Pat. No. 3,641,965. A fixed resistor 86 is connectedbetween the input terminal of the comparator forming the commonconnection to the position sensor and the regulated power supply. Thefixed resistor 86 and the variable resistor 85 constitutes a variablevoltage dividing network with the variation of the lower leg beingdirectly related to the angular displacement. With the seriesresistances connected to the regulated voltage supply, a non-linearoutput with angular displacements is generated at the common junction.Applicant has found that the voltage output varies approximately as asine wave with angular displacement, at least over the limited number ofdegrees encountered for marine propulsion units such as stern driveswherein the movement covers essentially 55 of displacement. The voltagedividing network as described defines a curve which very closelyapproaches the sine wave curve and thus is completely suitable fordirect substitution for the Hall cell circuit shown in FIG. 3. Further,the variable resistor 85 is adjusted to create an offset signalcorresponding to a zero degree positioning of the drive unit 1 tostimulate the offset adjustment of the Hall cell, with the sine wavegenerated from that zero reference position.

When a resistive sensor is employed, an open circuit condition may becaused by the wear of the unit, water contamination, corrosion and thelike. If the sensing circuit does open, the voltage applied to the inputof the comparator from the regulated voltage supply rises as a result ofthe very high impedance presented by a total or partial maximum opencircuit between the input terminal and ground. This would, of course,create a maximum turn on lower signal at the sensing output lineconnected by resistors 47 and 47a to the comparator 20 which in turnwould lower the drive unit 1 to its lowermost position, with no means atthe control of the operator for reversing or running the drive unit 1 toa lower position. Such a malfunction may create a particularly dangerousposition under operating movement of the watercraft. To prevent thistype of condition from arising, a safety circuit 82 is interconnectedinto the control system and in particular responds to an abnormal inputvoltage to positively prevent the lower system from being turned on.

The fail-safe circuit 82 in the illustrated embodiment of the inventionis connected to the circuit of lowering amplifier 41 and particularlyline 87 to the base of transistor 61' and to the sensor signal line 32ato the comparator resistors to hold line 87 at ground in response to anabnormally high input voltage at the sensor power terminal or line andthereby prevent turning on of the lower switch 23a and the associatedrelay 68.

More particularly, the fail-safe circuit 82 includes a single high betatransistor 88 connected between the line 87 and thus the base oftransistor 61' and ground. A Zener diode 89 in series with resistor 90connects the base of transistor 88 to the sensor line 91.

A small capacitor 92 is connected between the resistor and ground whichdefines an inegrating circuit holding the fail-safe circuit in the offcondition for a momentary initial period of time with the input voltageabove the 8.8 volts reference level. This is desirable to preventactuation of the fail-safe circuit 82 during momentary or transientperiods of abnormal voltages. Thus, in the usual wound resistor unit,the wiper 84 loses contact in moving from one winding turn to the nextand would do so in the preferred linear resistor unit described. Zenerdiode 89 would be selected to provide a threshold detection of thevoltage when it rises above a selected level greater than the voltagenecessary to null the maximum voltage from the reference or selectionunit 17. When diode 89 conducts, current is supplied to the transistor88 which shorts the input to the lower circuit to ground. Thus, with a9.2 volt regulated supply and a maximum input reference signal of 7volts, the Zener diode 89 may be conveniently selected to respond to asignal of 8.8 volts.

The fail-safe circuit may take any voltage sensitive form which willdetect an abnormal high voltage on the input of the sensor circuit orthe like and positively prevent the malfunctioning of the circuit tolower the stern drive unit 1, particularly under running conditions. Forexample, a differential amplifying circuit may compare a fixed voltagewith that at the sensor line and control a control switch in the lowerdrive circuit.

The circuit of F 1G. 7 otherwise functions in the same manner as thatpreviously described to provide an automatic raising and lowering of thedrive unit to various trim positions as a result of the simple inputselection by the operator.

Further, the relatively large number of selections which can be madepermit the positioning of the drive unit in a proper position underessentially all possible operating conditions.

In addition to the electronic signal processing, the trim control canemploy a relatively simple comparison network for actuating of the trimpositioning motor or the like. For example, FIG. 8 illustrates a simpledifferential relay system.

In FIG. 8, a control rheostat 96 and a trim indicator rheostat 97 haveone end connected in common to the battery 98 and related movable tapsconnected to selectively energize a differential relay 99. The controlrheostat 96 is mounted for manual adjustment. The trim indicatorrheostat 97 is coupled to the drive unit for example as shown inpreviously referred to US. Pat. No. 3,641,965. The rheostat taps providecorresponding power signals in accordance with a desired trim angle andthe actual trim angle.

The differential relay 99 includes a first winding 100 connected inseries with the rheostat 96 and energized accordingly. The winding 100is electromagnetically coupled to one end of an armature 101 which iscentrally pivoted at 102. The armature 101 is, generally, a T-shapedmember which is connected by a line to battery 98 and with the stemportion carrying suitable contacts including a first set of contacts 103which are closed upon predetermined pivoting of the armature 101 towardthe electromagnetic unit defined by winding 100. An opposed winding 104is similarly connected into circuit with the rheostat 97 and is coupledto the opposite end of the armature 101. The electromagnetic force ofthe winding 104 tends to pivot the armature 101 in an opposite orcounter-clockwise direction as viewed in F IG. 8. Selected pivotalmovement in this direction results in closing of an oppositely disposedset of contacts 106. Thus, if the currents through the windings 100 and104 are balanced or essentially balanced, the armature 101 is held in acentral position with contacts 103 and 106 both open. Differentialenergization of windings 100 and 104 results in the closing of contacts103 or 106 to provide corresponding energization of a pair of powerrelays 107 and 108. The power relay 107 is connected to the one side ofthe contacts 103 and ground such that when the contacts 103 close, poweris supplied to the power relay winding 107 to close a related set ofcontacts 107-1. Similarly, power relay 108 is connected in circuitthrough the contacts 106 to control a related set of contacts 108-1. Thecontacts 107-1 and 108-1 are connected respectively in series with thecorresponding forward and reverse windings of a reversible motor 109,for corresponding controlled energization thereof. The motor 109 iscoupled to drive a pump 110 which in turn provides circulating fluidthrough an up-trim line 111 or a down-trim line 112 in accordance withthe directional energization of the motor 109. The down-trim lineincludes a surge valve 113. ln accordance with a further novel aspect ofthe present invention, a differential pressure switch 1 14 is providedin the energizing circuit of the motor 109 to momentarily remove theautomatic trim control under log jumping conditions. The differentialpressure switch 114 includes a pressure sensor 115 which is connected inparallel with the surge valve 113. The pressure sensor 115 is coupled tocontrol a normally closed switch 116 which is connected between ground117 and the ground side of the motor 109. lf a back pressure is createdon the drive unit resulting in a greater pressure on the down side lineof the actuator in excess of the pump pressure at line 1 12 and thus anet back pressure, the switch 116 opens. This effectively opens thecircuit for the control and permits the lower drive unit to moveupwardly in a relatively unrestricted manner to clear an obstruction.

The operation of the embodiment shown in FIG. 8 is otherwise generallysimilar to that previously described. Thus, the current flow of the twowindings of the differential relay 99 is in accordance with theresistance in the respective branches which in turn is proportional tothe desired setting and the actual trim setting, with the current in theone coil or winding greater than in the other in an amount equal to therelay threshold leve, the corresponding contacts 103 or 106 close toprovide corresponding energization of the appropriate power relay 107 or108. This, of course, establishes the desired operation of the trim pump1 10 to readjust the trim angle until such time as the trim anglesensing rheostat 97 again equals the preset rheostat 96. This thenre-establishes the null condition with the trim unit at the desiredposition.

As in the previous systems, any disturbance or oil leakage may result ina corresponding change in the trim angle from the dial setting. Thisagain operates the trim angle control to automatically reset the system.

Further, various safety features can, of course, be incorporated intothe trim setting control of this invention. For example, an interlockrelay may be interconnected to open when the ignition switch is turnedoff with a required manual reset switch. The interlock relay wouldremove the system until such time as the manual reset seitch ispositively actuated. A simple onoff switch could, of course, be providedwith reliance on the operator to turn off the switch whenever theignition system is turned off. For emergency use, a direct overridecontrol could be provided at the trim pump to permit desired positioningif the automatic system malfunctions or the like.

In addition to the illustrated sensing devices, any other suitablesensors can be employed. For example, inductive and capacitive sensorscan be readily applied within the broadest concept of the presentinvention as well as various photo devices such as photoresistive andphotoemissive devices. Further, although the control setting dial isshown on the instrument panel of the boat, it may also be incorporatedin the throttle control, the steering wheel hub or the steering columnfor convenient manipulation by the operator. It may also be desirable tohave the control setting dial constructed to provide automaticindication of the setting position through the sense of touch by theoperator such that he can maintain complete visual attention to thedriving of the boat.

Various other designs can, of course, be incorporated in connection witheach of the particular portions of the circuit and the like althoughthat illustrated has been found to provide satisfactory operation. Itmay be desirable to employ a suitable stop means to prevent selection ofthe two uppermost positions while under power and thereby eliminate thepossible danger of moving the drive unit (when running) upwardly out ofthe water. Other mechanical or electrical interlocks, not shown, canalso be readily designed into the system to prevent such selection.

These and similar features can, of course, be readily provided for thoseskilled in the art and thus no further particular discussion orillustration thereof is given.

The present invention has been found to provide a relatively simple andreliable trim power control system and apparatus.

Various modes of carrying out the invention are contemplated as beingwithin the scope of the following claims, particularly pointing out anddistinctly claiming the subject matter which is regarded as theinvention.

I claim:

1. A Hall cell sensor for producing a sine wave signal proportional totilt positioning of a pivotally mounted outboard drive unit, comprisingHall cell having a tubular housing having attachment means forsupporting the housing in fixed relation with respect to the outboarddrive unit, an annular magnetic means adjacent to said Hall cell andhaving attachment means for securing the magnetic means to the outboarddrive unit coaxially with the axis of rotation of the drive unit, saidmagnetic means being diametrically magnetized to produce an operativeflux field varying as a sine wave with angular orientation.

2. The Hall cell sensor of claim 1 wherein at least one of saidattachment means is adjustable to produce offset of the cell voltage.

3. The Hall cell sensor of claim 1 including a differential amplifierconnected to the output of the Hall cell and establishing a pair offloating output lines, a dual input operational amplifier, a pair ofemitter follower circuits connecting the pair of floating output linesto the operational amplifier, said operational amplifier including aresistivecapacitive feedback network, a resistive bias adjustment to theHall cell to establish a selected offset of Hall cell voltage, aregulated voltage supply, and a low-pass filter network connecting saidHall cell and said amplifier to the regulated voltage supply.

4. The Hall cell sensor of claim 1 wherein said housing includes arecess within which said Hall cell and a signal processing circuitcomponents are mounted and interconnected, a potting material fillingsaid recess to support said cell and circuit components, the housinghaving a wall adjacent the magnetic means which is non-magnetic.

5. The Hall cell sensor of claim 4 wherein said wall is formed of asolid material which is non-magnetic.

6. The Hall cell sensor of claim 4 wherein said circuit componentsinclude a differential amplifier connected to the output of the Hallcell and establishing a pair of floating output lines, a dual inputoperational amplifier establishing a single ended output signal, a pairof emitter follower circuits connecting the pair of floating outputlines to the second operational amplifier.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTIONPATENT NO. 3, 894,250

DATED July 8, 1975 INVENTOR(S) 1 JAMES R. HAGER and HUGH E RIORDAN It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 1, Line 37, after "setting" cancel "time and insert trim Column15, Line 5, after "reset" cancel "seitch" and insert switch Column 16,Line 24, before "feedback" cancel CLAIM 3 "resistivecapacitive" andinsert resistive capacitive Sign! and Scaled this second Day ofDeoember197$ [sen] A nest:

RUTH C. MASON C. IARSIIALI. DAMN Altestmg Officer (ommissiuner afferent:and "Ideal-1h

1. A Hall cell sensor for producing a sine wave signal proportional totilt positioning of a pivotally mounted outboard drive unit, comprisingHall cell having a tubular housing having attachment means forsupporting the housing in fixed relation with respect to the outboarddrive unit, an annular magnetic means adjacent to said Hall cell andhaving attachment means for securing the magnetic means to the outboarddrive unit coaxially with the axis of rotation of the drive unit, saidmagnetic means being diametrically magnetized to produce an operativeflux field varying as a sine wave with angular orientation.
 2. The Hallcell sensor of claim 1 wherein at least one of said attachment means isadjustable to produce offset of the cell voltage.
 3. The Hall cellsensor of claim 1 including a differential amplifier connected to theoutput of the Hall cell and establishing a pair of floating outputlines, a dual input operational amplifier, a pair of emitter followercircuits connecting the pair of floating output lines to the operationalamplifier, said operational amplifier including a resistivecapacitivefeedback network, a resistive bias adjustment to the Hall cell toestablish a selected offset of Hall cell voltage, a regulated voltagesupply, and a low-pass filter network connecting said Hall cell and saidamplifier to the regulated voltage supply.
 4. The Hall cell sensor ofclaim 1 wherein said housing includes a recess within which said Hallcell and a signal processing circuit components are mounted andinterconnected, a potting material filling said recess to support saidcell and circuit components, the housing having a wall adjacent themagnetic means which is non-magnetic.
 5. The Hall cell sensor of claim 4wherein said wall is formed of a solid material which is non-magnetic.6. The Hall cell sensor of claim 4 wherein said circuit componentsinclude a differential amplifier connected to the output of the Hallcell and establishing a pair of floating output lines, a dual inputoperational amplifier establishing a single ended output signal, a pairof emitter follower circuits connecting the pair of fLoating outputlines to the second operational amplifier.